BiffVernon Blogspot

Saturday, July 14, 2012

Turning out nice?

Since the industrial revolution our burning of fossil fuels,
coal, oil and gas, has increased the concentration of carbon dioxide in the air
from below 300 parts per million to about 400 ppm. The physics that was worked out in the 19th
century tells us that an increase in global temperatures is the inevitable
result. So far global average surface
temperatures have increased by just under 1° C.

Surface temperatures have not increased evenly; the warming
has been much greater in the Arctic than at lower
latitudes. Our weather is strongly
affected by the strong high level winds, the jet stream. The position and strength of the jet stream
determines whether rain producing depressions pass over southern England
or northern Scotland
or are blocked from reaching us.

As the Arctic warms we get a lower
temperature gradient between the Equator and the Pole. This results in a tendency for the jet stream
to be weaker and more meandering, and this in turn tends to block weather
systems. The result is longer periods of
continuous wet weather or continuous fine weather; more floods and more
droughts.

The frequency of such extremes has increased in recent
years, right across the northern hemisphere.
It’s just what we expected.